(a) Field of the Invention
The present invention relates to apparatus for the production of small dental prostheses by means of quadrant impression carriers.
(b) Description of the Prior Art
Quadrant impression carriers are intended to allow the production of small prostheses, of one to four teeth at the maximum. They allow an impression to be taken with closed mouth, without producing any risk of vomiting by the patient.
The impression thus achieved, utilising a silicone polyether or polysulfide impression paste, for example, serves for the production of a plaster cast which is then used on an occlusor to enable the production of the artificial tooth or teeth of the prosthesis.
The occlusor, in contrast to an articulator, has a movable arm which can effect only an oscillatory movement about its axis while the movable arm of an articulator has several degrees of freedom.
The use of an occlusor presents the drawback of not enabling the actual movements of the lower jaw to be reproduced, movements which comprise not only a rotation but also a lateral displacement (movement of Bennett).
Hence the prostheses produced utilising such occlusors require adjustment in the mouth, which has to be effected by the dentist, which can be complex and must be much more important when the material from which the prosthesis is made is less ductile, which is especially the case with the porcelains which are becoming more and more frequently used, and which do not adjust themselves during wear.